reza sayah, cairo. >>> and tension is rising again in gaza and 6 minutes what israeli satellites or thely saw. >>> authorities in massachusetts say they know what triggered that massive natural gas explosion we first showed you on friday. this blast leveled buildings and injured dozens in springfield massachusetts. they say a utility worker accidentally punctured a pipe about an hour before that explosion. >> if there is a certain level of gas to air mixture, then it's what is called an explosive level, he and at that point any ignition source can set the detonation and that could be a spark. that could be a telephone ringing. that could be a doorbell. >> 20 people were hurt. no one seriously. authorities say most of those injured were gas workers, firefighters and police officers who ducked for cover behind a utility truck just before the blatch. >>> authorities in mountainview caught up with a s.w.a.t. team this morning an armed man barricaded himself inside his girlfriend's apartment. police say richard johnson locked himself into the apartment after he hit his girlfriend. the girlfrie